Conventional golf balls typically comprise two functional components: a core and a cover. The primary purpose of the core is to be the “spring” of the ball or the principal source of resiliency. The cover protects the core and provides feel and greenside performance.
Two-piece solid balls are typically made with a solid core, usually made of a cross-linked polybutadiene or other rubbers, encased by a hard cover material. The core and/or the cover may also comprise multiple layers.
In an effort to make golf balls with improved performance characteristics, manufacturers have added fillers in various layers of the multi-piece golf balls. Fillers are typically added to adjust the density, rotational moment of inertia, flex modulus, mold release, or the melt flow index of one or more layers. For example, adding fillers to thermoplastic layers increases the flexural modulus or stiffness of such layers, so that the golf balls may achieve lower spin rates and greater distances.
Fillers used in the golf ball art typically include fibers, inorganic powders, carbonates, metal and metal alloys, metal oxides, metal stearates, particulate carbonaceous materials and micro balloons. Fibers typically include glass fibers, aramid fibers and asbestos. Inorganic materials typically include silica, clay, talc and mica. Metal and metal alloys typically include titanium, tungsten, aluminum, bismuth, nickel, molybdenum, iron, steel, lead, copper, brass, boron, zinc and tin, among others. Metal oxides typically include zinc oxide, iron oxide, aluminum oxide, titanium oxide and magnesium oxide. Metal stearates typically include zinc stearate, calcium stearate, barium stearate, lithium stearate and magnesium stearate. Particulate carbonaceous materials typically include graphite, carbon black, natural bitumen, cotton flock and cellulose.
The fillers are typically mixed or blended in a finely divided form with polymeric material, or are mixed with the monomers prior to polymerization to react and become part of the polymer. However, some of these fillers, such as graphite, have nanostructures that have not been fully utilized in the golf ball art. Up to now, graphite is typically delaminated into single-layer platelets with various aspect ratios for dispersion into a polymeric matrix for use as a layer(s) on the golf ball. Hence, there remains a need in the art for a golf ball having improved filled layers.